The present invention relates generally to fluid pumps and is particularly concerned with rotary disc pumps in which a plurality of rotating discs are used to pump fluid.
Rotating disc pumps of this general type are described in my U.S. Pat. Nos. 4,768,920 and 4,773,819. In both patents, a pump is described which comprises a plain disc impeller with a substantially unobstructed passage between the inlet and outlet of the pump. The fluid is pumped through the pump by means of friction or viscous drag and shear forces created by the rotating discs. The open design of the pump, with clearances between the opposing flat disc faces, allows fragile materials or articles carried along in a fluid stream to be pumped, which would not be possible in more conventional vaned rotor pumps in which the vanes act as impellers forming a channel for the fluid. The plain disc pump is suitable for pumping both fragile and severely abrasive materials, highly viscous fluids, and fluids with a high solids content, which would otherwise cause damage to close-fit impellers and vanes on more traditional vaned or bladed rotor pumps. However, the plain disc pump has a lower flow rate and efficiency than a bladed rotor pump.